default definitions for Lua

defdef.lua

-- defdef.lua
-- default definitions for lua
-- By Robin Wellner (gvx)
-- I hereby waive copyright and related or neighboring rights to this work
-- See the Creative Commons Zero Waiver at <http://creativecommons.org/publicdomain/zero/1.0/>


-- Evaluate truth like in Python
function is_true (arg)
	if arg == '' or arg == 0 then
		return false					-- empty string or zero returns false
	elseif type(arg) == 'table' then
		for k, v in pairs(arg) do
			return true					-- non-empty table returns true
		end
		return false					-- empty table returns false
	else
		return arg						-- all else is evaluated by lua
	end
end


-- Print a table
function printtbl(tbl)
	for k,v in pairs(tbl) do
		print(k .. ': ' .. v)
	end
end


-- Print a sequence
function printseq(tbl)
	for k,v in pairs(tbl) do
		print(v)
	end
end


-- Sequence "type"
function seq(tbl)
	local mt = {tostring=function () '['..table.concat(tbl, ', ')..']' end}
	setmetatable(tbl, mt)
	return tbl
end